Resistance apparatus for converting mechanical movement into electrical pulses



June 7, 1949. E L JR 2,472,770

RESISTANCE APPARATUS FOR CONVERTING MECHANICAL MOVEMENT INTO ELECTRICALPULSES Filed NOV. 20, 1945 INVENTOR L eoLHelterline Jr. M

- ATTO R N EY sound as recorded. h I

which varies" Patented June 7, 7949 "cimm'sns AP ARATUSFOR'CONVEIWMGMovEMEN'rlmmo-EmomL El'ectrleProducts lnc sitlemjMals corporationlbtsMassaclmsetts e acilfistsmei em l range of tilt! o-ifiquhcies. s

'fiirthei obiectibf :h-ifitefitibm is" 5 m .Ii'i'o'i i'de a. soundrecord niodiiliztbr' 'ihavinrincreased .power outfiut. I I

"*A fu'rther dbieot bf' th ihi'eiitiori'isto provide 'a sound record"Heidi-device having greatly reduced un eusnee ene;:nawre of which issubstsnda-ny an iihin'i "resistance. 7

*Other' objects 'h'nd ieitizies willfm'bre "fully 'appear from thefollowing descri'fitfon andwill be particularly pointed out in thecreams.

The biesent"invention conifiiises essentielly an electric circuit heg'*therein 'a source "of energy, i lo'ad' impedance n snsenigymaauiatmg-aeview-consisting 619', ontiot ribai'rierimpedancefifiifiiii'ctio pi'essiire aiid means for 'n ichan'fally vsrymmh prssureon the 1 idifi ihibedaiice.

s'uitapifimiiedgnee llliisttetd' rierin I theg-type sir'ggested iswnerelm metallic cimtasting "'eng ages en electric-any conductivecrystal.

be iit'ilizedto seventeen-laureate: oft-suitable type for 'vis-ual"ofiaiidioobsertttion.

described and-illustrated in the drawings'iin non-serum airecotd -rehdicam-rem iti'into a. mo'du- 'HtedQbOtefiiiiaI;

siiitnemsamior ruga susa diag ra' minatic fldewiliustriting"theappli'c'ation o'f the ihVeiition =t6therD1ddizb6ion ofsound.

The invention has various applications-where it *is 'desired to provideai sensitive aridreadily perceived response to slig'ht.nieehanicaHmovementsor pres-sures sucnasdn mee'hanicai'--'strain gaugesoiin delicateend flizcflratEfi-inifisidnal gauging-apparatus.

A partieul-ar- (re licationdescribed and illustrated herein "in' which-thewrineipiefinvoivedi is al pl ied' to ai'sour'id 'tecolid pidkudevice.

-The particular embod ment Hown isincorberated I in -a convemimiaiesound-i-ecord epparatus such as used for entertain'm nfipurposes andconsisting of a eabmet =i=-iv hirr' whichris received a means :fordriviii'th tilmtaibl 2 'and a sound rep'roducingfi apparetus"thesoundfrom which emergesat the--g rill workiopenipg '3. A tone arm 4- issuspended iii-the usual -'m'anner' and adapted to carry" an enei 'gy"modulates-meme er' S embodyingthe' ii'ive'nt'ion "File-member 5 issupportedin-the 'fr'ee' eiid o the-tone airmfin'positionto engage a'fsouii'dere'cbrd 6-"' upon the turntabled.

The energy modulate? -5= desirab1y is enclosed in acas'ing T or suitablematerials-auditorconveliience in= asseiiibling is oomp'o'sjd of twoseparable'sec-tion's' held to'geth'ei by screws 8. Within the casingiS-re'ceiVed a i'otatabledrivingshaft 9 supported atits' 'enHsdntheeasing. '-.The' shaft 9 receives impulses from th re'cord 5 which=has alatemlly out" soundq g-roove 1 11 ther'ein. II -he impulses aretransmitte'd -toi the FShiffiby, the needle H secured iifth-shait.'ThenG'edIe-may be replaceable or ma'y be -fdf the=-permanent -typehaving a -j'eweied tip -and f fiirediy secured" in the shaft.

i The impulses at the 'shaft are" iii-the =form-"-of short rotativoscillations which are in "turn transmitted to an' -a'rm 12 rigidlysecured -'to and extending out i-1 0m the.= 'sh-aft atsub'stantiaIIy"from the needle -At-the*-io1iterend" of the arm I z is secured a wire 30? condu'ctive'metal cominto a form to provide resilience and has astraight portion 'atrvi't's-kbdttome'rid' which resib iently engages thesiirfece OP e piece *of electri- Cally 1 conductive' ci'y-s'tm '14.""-Ehe -'-elen'ient'- may be silicon -germanium or other material whichwill constitute a "cont'eicti or liarrier type impedance wli-ich-avariesas'adunctiomof pressure, andis prov iiied ?with? electricalr'connectionin the for-nibfa mefialil fcehoidei' f5 td-Tivhi'ch afleadwire 16 is secured. Desirably tl'i hfilfler lifls 3 adjustable axiallyof the wire l3 within the easing l. Any suitable means may be used tohold the element M in adjusted position such as the set screw II.

By way of example the member l4 may be a crystal the face of which isarranged substantially upon a'plane passing through the axis of theshaft 9 and the straight portion of the wire [3 is perpendicular to thecrystal face. This 1 arrangement of crystal and wire provides truestraight line action in operation.

The casing 1 is provided with a chamber [8 to provide space for theelements of the device and an opening [9 is provided in, the casingWithin which the needle moves. the shaft 9 are received in rubberbushings 20 which are in turn received in closely fitting apertures inthe casing. By thus supporting the shaft undesirable vibrations areeliminated due to the snubbing action of the rubber. To further controlunwanted vibration-s a pad of rubber 20m may be inserted between theupper surface of the arm l2 and the wall of the chamber I8. To completethe electrical circuit through the device a flexible lead wire 2! isconnected to the wire l3. The connection to thewire is desirably madethrough the shaft 9 and arm is by soldering the wire to one end of theshaft. The lead wires l6 and 2| are lead through the tone arm andconnected in the electrical circuit of the apparatus. The energymodulator may be supported in the tone arm in any desired manner such asby means of screws 22 passing through the casing l and having threadedengagement with the top wall of the tone arm.

Fig. illustrates one manner in which the modulator member may beemployed in a sound reproducin apparatus. The modulator is connected inseries in a circuit 2 3 containing a load resistor 25 and a directcurrent source such as the battery 26. An output connection is made fromone end of the resistor 25 to a blocking condenser 21 of suitablecapacity which in turn is connected to one or more stages of audioamplification. It may be found desirable to change the relative positionin their circuit and the values of the resistor 25, the battery 25 andthe condenser 21 to obtain a desired circuit characteristic. One audiostage is shown and any suitable means may be employed to couple themodulator thereto. As shown the blocking condenser 2i is connected to acoupling impedance 28. The varying potential at the impedance isconducted to the control grid of an amplifier-tube 29 by means of aconnection 30. The output of the tube is conducted to a suitable sounddevice such as the loud speaker 3i through a suitable couplingtransformer. The tube and loud speaker are supplied with operating powerin any desired manner not shown.

An A. C. source of current may be used in place of the battery 26. Sucha source may have a frequency of from approximately 10,000 cycles to 100megacycles. In this case the material for the member it must be capableof functioning as a rectifier as well as a modulator.

The impedances and condenser may be of any suitable value. The impedancemay be fixed or variable and may be of the order of 1000 ohms to one ormore megohms. The D. C. source may supply any voltage, desirably 100volts or less. The impedance 23 may be fixed or variable and may be ofthe order-of 3% megohm and the condenser 21 may have a capacity ofsubstantially -.0 icr fa ed- Desirably the ends of For best performancethe position of the crystal [4 should be adjusted to provide a firmpressure of the wire I3 upon the crystal. In operation the resiliency ofthe rubber bushings 20 and the pad 204:: permits the record 6 to causethe arm l2 to move up and down which varies the pressure of the wire itupon the rystal which in turn varies its resistance and. therebyproduces a potential across the impedance 25 which varies in accordancewith the original sound as recorded on the record. The varying potentialis amplified by the tube 2'! and converted into sound by the loudspeaker 29.

The operation of the apparatus is highly efficient and produces highlyaccurate reproduction of a desired band of audio frequencies. Acontributing factor inits efficient operation is the relatively lowimpedance of the crystal and wire combination which is of the order of10,000 ohms. This impedance is very low compared to other devices of asimilar nature. For example, a piezoelectric modulator device may havean impedance as high as 10 megohms at audio frequency. The sound pick updevice of the present invention therefore makes available as much as onehundred or more times the power developed by other types of pick updevices.

Another advantageof the invention is the fact that the modulatormemberpresents an impedance which consists practically entirely of ohmicresistance. The invention thereby eliminates stray capacity andinductive factors. Thus it becomes unnecessary .to introducecompensating elements in the circuit. The invention therefore is capableof very accurate operation and moreover permits greatflexibility in thedesign of circuits in which it may be used.

It has been found that very efficient crystals for use in the apparatusare a silicon crystal having aluminum dispersed therein or a germaniumcrystal having tin dispersed therein as disclosed in the copendingapplication of E. T. Casellini, Serial No. d92,163, filed June 23, 1943,for Electrical. rectifiers. I

What I claim is: v i

. 1. In an apparatus for producing electrical impulses from a soundrecord having a groove therein, a modulator member comprising a casingan operating shaft supported in the casing for slight rotativeoscillating movement, a sound record having a sound groove therein, apointed needle engaging the sound groove and acting to move theoperating shaft in accordance with the sound record in said groove,anarm secured to and extending outward from the shaft, a resilient wiresecured to the outer end of said arm. a semi-conducting member having aface thereof disposed in engagement with said wire said semi-conductingmember having the characteristic of varying the impedance of its contactwith said wire in accordance with varying pressure applied thereto,

and electrical connections from said wire and semi-conducting member forconnection in a circuit. n a r 2. In an apparatus for producinelectrical im-. pulses from a sound record having a groove therein, amodulator membercomprising a casing, operating shaft supported in thecasing for slight rotative oscillating movement, a sound record having asound groove therein, a rigid pointed needle engaging the sound grooveand acting to move the operating shaft in accordance with the soundrecord in the groove, an arm secured to the shaft, a resilient wiresecured to. the outer end of the arm,- an electrically conductivecrystal mounted in the casing having its face disposed in engagementwith and substantially perpendicular to said wire and electricalconnections from said wire and crystal for connection in a circuit.

3. An apparatus defined according to claim 2 in which the crystal is ofsilicon having aluminum dispersed therein.

4. An apparatus defined according to claim 2 in which the crystal is ofgermanium having tin dispersed therein.

5. In an apparatus for producing electrical impulses from a sound recordhaving a groove therein, a modulator member comprising a casing, anoperating shaft supported in the casing for slight rotative oscillatingmovement, a pointed needle engaging the groove in said record and actingto move the operating shaft in accordance with the groove in said soundrecord, a semiconductor member having the characteristics of varying itsimpedance in accordance with the pressure of a contact on its surface, acontact to said surface, said contact being one. end of a resilientwire, means connecting another part of said resilient wire to saidoperating shaft to vary the pressure exerted on said resilient wire inaccordance with the movementfof'said shaft, and electrical connectionsfrom said wire and said semi-conducting member forccnnec'tion in acircuit.

LEO L. HELTERLINE, Jn.

REFERENCES CITED The following references areof record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Proc. of the Natl. Acad. ofSciences, vol. II, 1-925, pp. 743 to 748.

